The present invention relates to a filler which is small in a change in weight in both of oxygen (O2) plasma treatment and CF4 plasma treatment to be carried out without fail in production process of semi-conductors and can remarkably inhibit generation of foreign matters (micro-particles) in the plasma treatments, and also relates to a crosslinkable elastomer composition containing the filler and to various materials and various final products which are produced from the composition.
In production of semi-conductors and liquid crystals, various treatments are carried out by using various plasmas such as oxygen plasma and CF4 plasma at the stages of CVD, dry etching, ashing, etc. of silicon wafer. In the treatment equipment employing those plasmas, elastomeric sealing members are used for sealing of various connecting parts and moving parts of the equipment. Those sealing members are required not only to have a sealing property but also as a result of microfabrication and the advent of a large-sized substrate wafer, to stand strict high density plasma treating conditions (1012 to 1013/cm3) and not to contaminate semi-conductors which require very precise fabrication. To satisfy such requirements, a crosslinkable fluorine-containing elastomer and silicone elastomer are used as elastomeric materials for sealing members.
Since a sufficient mechanical strength cannot be obtained even if only an elastomer is crosslinked, an organic or inorganic filler is usually blended. However even a filler is required to have the above-mentioned properties (neither decomposing nor generating a foreign matter, etc.). It cannot be said that any fillers can be used. Examples of fillers which have been used or proposed are carbon black, silica (Japanese Patent Publication No. 2783576, Japanese Patent Publication No. 2858198), polytetrafluoroethylene (PTFE) powder, titanium oxide powder, clay, talc, barium sulfate, and the like.
However some of those fillers (silica, titanium oxide, etc.) are stable in oxygen plasma treatment but are decomposed to cause a reduction in weight in CF4 plasma treatment, and on the contrary, some of them (carbon black, PTFE powder) are stable in CF4 plasma treatment but are decomposed to cause a reduction in weight in oxygen plasma treatment. If the filler is subject to a change in weight, particularly a reduction in weight by plasma irradiation, it is certain that a reduced portion becomes an unnecessary foreign matter and has any adverse effect on semi-conductors and liquid crystals. Thus the above-mentioned fillers have been proposed. However a state of a change in weight differs depending on kind of the filler and no fillers being stable in the both plasma treatments have been known.
An object of the present invention is to provide a filler which is stable and is very small in a reduction in weight in both of oxygen plasma treatment and CF4 plasma treatment, and a crosslinkable elastomer composition, etc. comprising the filler and a crosslinkable elastomer.
Namely the present invention relates to the filler for crosslinkable elastomer, in which a change in weight of the filler after either of oxygen plasma irradiation and CF4 plasma irradiation under the conditions of a flow rate of 200 sccm, a pressure of 280 mTorr, a RF output of 400 W and an irradiation time of 54 minutes is not more than 4 mg/cm2 xc2x7hr, preferably not more than 1 mg/cm2 xc2x7hr.
It is preferable that the filler has a thermally and chemically stable aromatic ring on a trunk chain, has heat resistance of not less than 150xc2x0 C. and particularly comprises a synthetic high molecular compound having an amide bond on a trunk chain or a synthetic high molecular compound having an imide bond on a trunk chain.
A form of the filler of the present invention is not limited particularly. The filler can be used in various forms such as fiber, particle and flake.
Further the present invention relates to the crosslinkable elastomer composition comprising a crosslinkable elastomer and the above-mentioned filler.
It is preferable that the crosslinkable elastomer composition contains the above-mentioned filler in an amount of 1 to 150 parts by weight based on 100 parts by weight of the crosslinkable elastomer and that the crosslinkable elastomer is a fluorine-containing elastomer or a silicone elastomer.
Also the crosslinkable elastomer composition can be used as a crosslinkable elastomer material for molding or a crosslinkable elastomer material for coating.
When the composition is used as the material for molding, it is preferable that the composition contains 1 to 150 parts by weight of the above-mentioned filler and 0.05 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the crosslinkable elastomer.
When the composition is used as the material for coating, it is preferable that the composition contains 1 to 150 parts by weight of the above-mentioned filler and 0.1 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the crosslinkable elastomer.
Further the present invention relates to the molded article obtained by crosslinking the crosslinkable elastomer material for molding, particularly to the sealing member for sealing of semi-conductor production equipment.
Also the present invention relates to the coated molded article obtained by applying the crosslinkable elastomer material for coating on a surface of an elastomer molded article and then crosslinking, particularly to the sealing member for sealing of semi-conductor production equipment.
A change in weight of the filler for crosslinkable elastomer of the present invention after either of oxygen plasma irradiation and CF4 plasma irradiation under the above-mentioned conditions is not more than 4 mg/cm2xc2x7hr.
The above-mentioned standard conditions for plasma irradiation are set in consideration of actual treating environment for production of semi-conductors. It is assumed that under those conditions the results reflect an actual situation in the production site of semi-conductors. A change in weight under those irradiation conditions is preferably not more than 1 mg/cm2xc2x7hr.
Examples of a substance corresponding to the filler of the present invention are, for instance, imide fillers having an imide structure such as polyimide, polyamideimide and polyetherimide; organic fillers prepared from engineering plastics having heat resistance of not less than 150xc2x0 C. such as polyarylate, polysulfone, polyether sulfone, polyphenylene sulfide, polyether ether ketone and polyoxy benzoate; and the like.
Among them, preferable are the imide fillers from the viewpoint of heat resistance, a low metal content and a small amount of outgas generation.
Such a filler is blended to the crosslinkable elastomer to give the crosslinkable elastomer composition. A fluorine-containing elastomer and silicone elastomer can be used as the crosslinkable elastomer, and from the viewpoint of heat resistance, the fluorine-containing elastomer is preferable.
The fluorine-containing elastomer which can be used suitably in the present invention is not limited particularly as far as it has been used for sealing members, particularly for sealing members for semi-conductor production equipment. Examples thereof are, for instance,
a copolymer rubber represented by the formula (I): 
wherein m is 85 to 60, n is 15 to 40, a copolymer rubber represented by the formula (II): 
wherein m is 95 to 50, n is 5 to 50, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms, a terpolymer rubber represented by the formula (III): 
wherein 1 is 85 to 20, m is 0 to 40, n is 15 to 40, a terpolymer rubber represented by the formula (IV): 
wherein 1 is 95 to 45, m is 0 to 10, n is 5 to 45, X, Y and Z are fluorine atom or hydrogen atom individually, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms, and a terpolymer rubber represented by the formula (V): 
wherein 1 is 95 to 35, m is 0 to 30, n is 5 to 35, Rf is a perfluoroalkyl group having 1 to 8 carbon atoms. Among them, it is preferable to use the copolymer rubber represented by the formula (I) or (II) or the terpolymer rubber represented by the formula (III) from the viewpoint of chemical resistance, heat resistance and plasma resistance.
Further there are copolymers of an elastomeric segment copolymer with a non-elastomeric segment copolymer as the fluorine-containing rubber for fluorine-containing rubber sealing member of the present invention.
The elastomeric segment is a non-crystalline segment having a glass transition temperature of not more than 25xc2x0 C. Preferable components thereof are, for example, TFE/PAVE/monomer giving a curing moiety (45 to 90/10 to 50/0 to 5 in % by mole, hereinafter the same), more preferably 45 to 80/20 to 50/0 to 5, particularly 53 to 70/30 to 45/0 to 2.
Examples of the monomer giving a curing moiety are, for instance, vinylidene fluoride, iodine-containing monomers represented by CX2xe2x95x90CXxe2x80x94Rf3CHRI, wherein X is H, F or CH3, Rf3 is a fluoro alkylene group, perfluoro alkylene group, fluoro polyoxyalkylene group or perfluoro polyoxyalkylene group, R is H or CH3, 
wherein X is CN, COOH or COOR, in which R is an alkyl group of C1 to C10 which may have fluorine atom, m is 0 to 5, n is 1 to 3, bromine-containing monomers, and the like. Usually the iodine-containing monomers are suitable.
Examples of the copolymer which is a non-elastomeric segment are
(1) VdF/TFE (0 to 100/ 100 to 0), particularly VdF/TFE (70 to 99/30 to 1), PTFE or PVdF;
(2) ethylene/TFE/HFP (6 to 43/40 to 81/10 to 30), 3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene-1/PAVE (40 to 60/60 to 40);
(3) TFE/CF2xe2x95x90CFxe2x80x94Rf1 (amount exhibiting non-elastomeric property, namely, an amount of CF2xe2x95x90CFxe2x80x94Rf1 is not more than 15% by mole);
(4) VdF/TFE/CTFE (50 to 99/30 to 0/20 to 1);
(5) VdF/TFE/HFP (60 to 99/30 to 0/10 to 1);
(6) ethylene/TFE (30 to 60/70 to 40);
(7) polychlorotrifluoroethylene (PCTFE);
(8) ethylene/CTFE (30 to 60/70 to 40); and the like. Among them, from the viewpoint of chemical resistance and heat resistance, non-elastomeric copolymers, particularly PTFE and TFE/CF2xe2x95x90CFxe2x80x94Rf1 are preferable.
Examples of the silicone elastomer are, for instance, silicone rubber, fluoro silicone rubber, and the like.
In the crosslinkable elastomer composition, an amount of the filler of the present invention is from 1 to 150 parts by weight, preferably 5 to 100 parts by weight based on 100 parts by weight of the crosslinkable elastomer. When an amount of the filler is small, a mechanical strength is insufficient, and when too large, elongation is inferior.
The crosslinkable elastomer composition containing the filler is useful as a molding material for various molded articles and as a coating material for various elastomer molded articles.
The crosslinkable elastomer material for molding may be prepared by blending 1 to 150 parts by weight, preferably 5 to 100 parts by weight of the filler and 0.05 to 10 parts by weight, preferably 0.5 to 5 parts by weight of the crosslinking agent based on 100 parts by weight of the crosslinkable elastomer.
The crosslinking agent may be optionally selected depending on kind of crosslinkable group (cure site) of the crosslinkable elastomer.
The crosslinking can be carried out by, for example, peroxide crosslinking system, polyol crosslinking system, polyamine crosslinking system, triazine crosslinking system, oxazole crosslinking system, imidazole crosslinking system, thiazole crosslinking system, and the like.
For the peroxide crosslinking, any of known organic peroxides which generate a peroxy radical under vulcanization temperature condition may be used. Examples of the preferable organic peroxide are di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2, 5-di(t-butylperoxy)hexane, and the like.
Examples of the crosslinking agent for the polyol crosslinking are polyol compounds such as bisphenol A and bisphenol AF.
Examples of the crosslinking agent for the polyamine crosslinking are polyamine compounds such as hexamethylenediamine carbamate, N,N -dicinnamylidene-1 ,6-hexanediamine, and 4,4-bis(aminocyclohexyl)methane carbamate.
Examples of the crosslinking agent for the triazine crosslinking are organotin compounds such as tetraphenyltin and triphenyltin.
Examples of the crosslinking agent which is used in oxazole crosslinking system, imidazole crosslinking system and thiazole crosslinking system are, for instance, bisdiaminophenyl crosslinking agent represented by the formula (VI): 
wherein R3 is xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, an alkylene group having 1 to 6 carbon atoms, a perfluoroalkylene group having 1 to 10 carbon atoms or a single bond, one of R4 and R5 is xe2x80x94NH2 and another one is xe2x80x94NH2, xe2x80x94OH or xe2x80x94SH and preferably each of R4 and R5 is xe2x80x94NH2, bisaminophenol crosslinking agent, bisaminothiophenol crosslinking agent, bisamidrazone crosslinking agent represented by the formula (VII): 
bisamidoxime crosslinking agent represented by the formula (VIII) or (IX): 
wherein Rf3 is a perfluoroalkylene group having 1 to 10 carbon atoms, 
wherein n is an integer of 1 to 10, and the like. Those bisaminophenol crosslinking agent, bisaminothiophenol crosslinking agent and bisdiaminophenyl crosslinking agent have been used for a crosslinking system employing nitrile group as a crosslinking point, but are also reacted with carboxyl group or alkoxycarbonyl group to form an oxazole ring, thiazole ring or imidazole ring and give a crosslinked article.
Particularly preferable crosslinking agents are compounds having a plurality of 3-amino-4-hydroxyphenyl groups, 3-amino-4-mercaptophenyl groups or 3,4-diaminophenyl groups represented by the formula: 
wherein R3 is as defined above, R1 and R2 are the same as the above-mentioned R4 and R5. Examples thereof are, for instance, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (general term: bis(aminophenol) AF), 2,2-bis(3-amino-4-mercaptophenyl)hexafluoropropane, tetraamino benzene, bis-3,4-diaminophenylmethane, bis-3 ,4-diaminophenylether, 2 ,2-bis(3 ,4-diaminophenyl)hexafluoropropane, and the like.
An amount of the crosslinking agent is usually from 0.05 to 10 parts by weight, preferably 1 to 5 parts by weight based on 100 parts by weight of the crosslinkable elastomer. When less than 0.05 part by weight, the crosslinkable elastomer is not crosslinked sufficiently, and when more than 10 parts by weight, physical properties of crosslinked article are lowered.
When the crosslinkable elastomer composition of the present invention is used, particularly as a material for coating, a crosslinking aid such as a multi-functional co-crosslinking agent can be used. Examples of the multi-functional co-crosslinking agent are, for instance, bisolefins represented by triallylcyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triacryl formal, triallyl trimellitate, N,Nxe2x80x2-m-phenylenebismaleimide, diallyl phthalate, tetraallyl terephthalamide, tris(diallylamine)-S-triazine, triallyl phosphite, and N,N-diallyl acrylamide, 1,6-divinyldodecafluorohexane, and the like.
An adding amount of the crosslinking aid is usually from 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight based on 100 parts by weight of the crosslinkable elastomer.
When the content of the crosslinking aid is less than 0.1 part by weight, the crosslinkable elastomer is not crosslinked sufficiently, and when more than 10 parts by weight, elongation of the crosslinked article is lowered.
To the composition of the present invention can be added as case demands, additives which are usually added to a crosslinkable elastomer composition, for example, a filler, processing aid, plasticizer, coloring agent, and the like in a field where high purity and non-contaminating property are not required particularly. In addition to the above-mentioned additives, one or more of usual crosslinking agents and crosslinking aids other than the above-mentioned ones may be blended.
The composition and materials for molding and coating of the present invention can be prepared by mixing each of the above-mentioned components by using usual processing equipment for elastomer, for example, an open roll, Banbury mixer, kneader, or the like. In addition, the composition and the materials can be prepared also by a method of using a closed mixer and a method of co-coagulation through emulsion mixing.
For producing a pre-molded article from the above-mentioned composition and materials, usual known methods may be employed, such as a method of heating and compressing in a metal mold, a method of putting in a heated metal mold under pressure or a method of extruding with an extruder. In cases of extruded products such as a hose and cable, since shapes thereof can be maintained even after the extruding, a pre-molded article extruded without using a crosslinking agent can be used as it is. Of course, it is possible to use a pre-molded article subjected to crosslinking by heating with steam and using a crosslinking agent. Also in case of a shaped product such as O-ring, when it is difficult to hold a shape of the product in an un-crosslinked state after mold-releasing, it is possible to maintain the shape by using a pre-molded article crosslinked previously by using a crosslinking agent.
When carrying out peroxide crosslinking, the crosslinking can be carried out under usual crosslinking conditions for crosslinkable elastomers. For example, a crosslinked article can be obtained by putting a crosslinkable elastomer in a metal mold, carrying out press-crosslinking by holding under pressure at 120xc2x0 to 200xc2x0 C. for 1 to 60 minutes and then crosslinking in an oven by holding at 120xc2x0 to 250xc2x0 C. for 0 to 48 hours.
In the present invention when carrying out oxazole crosslinking by using a crosslinking agent such as bisaminophenol, the crosslinking can be carried out under usual crosslinking conditions for crosslinkable elastomers. For example, a crosslinked article can be obtained by putting a crosslinkable elastomer in a metal mold, carrying out press-crosslinking by holding under pressure at 120xc2x0 to 250xc2x0 C. for 1 to 60 minutes and then crosslinking in an oven by holding at 120xc2x0 to 320xc2x0 C. for 0 to 48 hours. Also to formulations of known crosslinking methods for crosslinkable elastomer such as polyamine crosslinking, polyol crosslinking and peroxide crosslinking, a crosslinking agent such as bis(aminophenol) AF is co-used to crosslink the elastomer.
Also imidazole crosslinking in which carboxyl group is crosslinked with bisdiaminophenyl crosslinking agent is optimum for a polymer containing carboxyl group at other point than end thereof, and gives a crosslinked article having good physical properties at a relatively low crosslinking temperature (for example, 150xc2x0 to 230xc2x0 C., preferably 1700 to 200xc2x0 C.).
In case of applications such as semi-conductor production equipment where non-contaminating property is strongly demanded, it is preferable to carry out crosslinking with a high energy ray without using a crosslinking agent. Examples of crosslinking source to be used are radiant rays such as xcex1-ray, , xcex2-ray, xcex3-ray and X-ray, electron beam, ultraviolet ray, and the like.
A quantity of radiation of high energy ray to be irradiated to the pre-molded article is, for example, in case of electron beam, preferably from 5 to 500 kGy, more preferably 10 to 300 kGy. When less than 5 kGy, an improvement in mechanical strength by irradiation of the electron beam is insufficient. When more than 500 kGy, deterioration of the elastomer advances and a part of bonds between the molecules is cut, thereby lowering a mechanical strength of the molded article. In order to increase the mechanical strength, a radiation rate is preferably not less than 500 kGy/hr, more preferably 1,000 kGy/hr or more.
The present invention relates to the molded article obtained by crosslinking the above-mentioned composition or molding materials. Further the present invention relates to the coated molded article obtained by applying the above-mentioned material for coating on an elastomer molded article and then crosslinking.
Though articles made of various elastomer materials can be used as the elastomer molded article to be coated, preferable are fluorine-containing elastomers and silicone elastomers particularly from the viewpoint of heat resistance.
The molded article and coated molded article of the present invention are useful as various molded articles in the fields shown in Tables 1, 2 and 3 on the following pages.
Particularly the molded articles of the present invention can be used built-in the following semiconductor manufacturing equipment.
1) Etching system
Dry etching equipment
Plasma etching machine
Reactive ion etching machine
Reactive ion beam etching machine
Sputter etching machine
Ion beam etching machine
Wet etching equipment
Ashing equipment
(2) Cleaning system
Dry etching cleaning equipment
UV/O3 cleaning machine
Ion beam cleaning machine
Laser beam cleaning machine
Plasma cleaning machine
Gas etching cleaning machine
Extractive cleaning equipment
Soxhlet extractive cleaning machine
High temperature high pressure extractive cleaning machine
Microwave extractive cleaning machine
Supercritical extractive cleaning machine
(3) Exposing system
Stepper
Coater and developer
(4) Polishing system
CMP equipment
(5) Film forming system
CVD equipment
Sputtering equipment
(6) Diffusion and ion implantation system
Oxidation and diffusion equipment
Ion implantation equipment
Among them, the molded articles of the present invention exhibit excellent performance as sealing members particularly for CVD equipment, plasma etching equipment, reactive ion etching equipment, ashing equipment and excimer laser exposing equipment.